Blow open moving contact assembly for electric power switching apparatus with a very high current interruption rating

Abstract

A moving contact assembly for a high-current interruption electric power switching apparatus has an inner carrier for the contact fingers that is rigidly held in a withstand position in an outer carrier by a spring biased cam follower pin engaging a cam profile on the inner carrier and configured to positively seat an inner carrier stop against an outer carrier stop on the outer carrier and to rapidly drive the inner carrier to a blow open position in response to a fault. The cam profile has an extended width divided between spaced apart cam profile sections to absorb the high closing and withstand forces. An abutment on the outer carrier resists bowing of the cam follower pin between the cam profile sections. Complementary convex and concave partial cylindrical surfaces on the inner carrier and a gas shield on the moving assembly carrier body maintain an arc gas seal during blow open.

1. A moving contact assembly for electrical switching apparatus comprising:
 a carrier body; 
 carrier legs supporting the carrier body for pivotal movement between a closed position and an open position; 
 an outer carrier secured to the carrier body; 
 an inner carrier having inner carrier sidewalls mounted on the outer carrier for pivotal movement between a withstand position and a blow open position and having an end wall with a cam profile, the end wall extending between the inner carrier sidewalls, and a cross wall having contact spring pockets and also extending between the inner carrier sidewalls; 
 a plurality of contact fingers pivotally mounted on the inner carrier; 
 contact springs seated in the contact spring pockets and bearing against the plurality of contact fingers; 
 a cam follower pin; 
 cam springs seated against the outer carrier biasing the cam follower pin against the cam profile which is configured so that for current through the contact fingers less than a threshold current, the inner carrier is biased to the withstand position and for current through the plurality of contact fingers greater than the threshold current, the inner carrier is rapidly driven to the blow open position; and 
 a gas shield associated with the carrier body and having a concave inner surface facing the cross wall of the inner carrier, the cross wall having a convex outer surface complementary to and in close proximity to the concave inner surface on the gas shield to maintain a gas seal as the inner carrier pivots from the withstand position to the blow open position. 
 
   
   
     2. The moving carrier assembly of  claim 1  wherein the cross wall on the inner carrier has contact spring pockets in which the contact springs are seated. 
   
   
     3. The moving carrier assembly of  claim 1  wherein the outer carrier has outer carrier sidewalls with elongated slots in which ends of the cam follower pin slide. 
   
   
     4. The moving contact assembly of  claim 3  wherein the outer carrier has cam spring pockets in which the cam springs are seated. 
   
   
     5. The moving carrier assembly of  claim 1  wherein the outer carrier has an outer carrier stop and the inner carrier has an inner carrier stop, the cam springs biasing the inner carrier so that the inner carrier stop engages the outer carrier stop to set the withstand position of the inner carrier. 
   
   
     6. The moving carrier assembly of  claim 5  wherein the cam profile has a withstand segment with a constant slope against which the cam follower pin bears with the inner carrier in the withstand position. 
   
   
     7. The moving contact assembly of  claim 6  wherein the cam profile has two spaced apart cam profile sections against which the cam follower pin is biased, the outer carrier having a base section with a medial abutment positioned to resist bowing of the cam follower pin between the cam follower profile sections with the inner carrier in the withstand position.